JP7189092B2 - radar equipment - Google Patents

Description

The present disclosure relates to radar equipment.

Millimeter-wave radars are known that are used for purposes such as automatic driving and collision prevention of vehicles. A millimeter-wave radar is a radar for detecting the existence of an object within a predetermined detection area and the distance to the object by radiating radio waves and detecting reflected waves of the radiated radio waves reflected by an object.

The performance of a millimeter wave radar deteriorates when it is mounted on a vehicle and evaluated as compared to when the radar is evaluated alone. This is caused by unwanted waves, which are radio waves that have deviated from the detection area or entered an unintended area, and become interference waves, disturbing the phase of the radar waves and causing errors in the azimuth detection of the object. A reflected wave from a bumper is known as a major unwanted wave.

Patent Literature 1 discloses a technique for suppressing multiple reflections of unwanted waves and reducing errors by providing an absorbing element made of a material that absorbs electromagnetic waves in a housing of a radar device.

Japanese Patent Publication No. 2015-507738

In the radar system described above, there is a problem that the manufacturing cost increases because the absorbing element needs to be installed separately from the radar system. In addition to the reflected waves from the bumper, unwanted waves radiated to the back of the radar also become interference waves when reflected by the vehicle body, creating a new problem of bearing detection errors.

In one aspect of the present disclosure, it is preferable to provide a radar device with a novel structure that reduces the azimuth detection error of radar.

One aspect of the present disclosure is a radar apparatus comprising an antenna section (2), radomes (4, 4a, 4c), and housings (3, 3b). The antenna section has an antenna surface on which one or more antennas that radiate radio waves are installed. The radome is made of a material that allows transmission of radio waves emitted by the antenna section, and is arranged to face the antenna surface. The housing forms a space for housing the antenna section together with the radome. At least a part of the peripheral edge of the housing surrounding the antenna surface and in contact with the radome has a barrier portion (32) protruding outward from the radome along the antenna surface.

According to such a configuration, by providing the barrier section, the unwanted waves propagating in the radome and radiated from the periphery of the radome are directed toward the rear surface of the radar device. It is possible to suppress the occurrence of an error in azimuth detection. Moreover, since there is no need to provide a radio wave absorbing element or the like to reduce direction detection errors, manufacturing costs can also be reduced.

In addition, the reflected wave from the barrier can also be an interference wave, but the influence can be dealt with by designing the radar device itself, so it changes according to the installation environment, and it is difficult to deal with the back side in advance. A direction detection error can be easily reduced compared to the influence of radiation waves.

It is a top view which shows the radar apparatus of 1st Embodiment. It is a top view of the state where the radome was removed in the radar apparatus of 1st Embodiment. FIG. 2 is a cross-sectional view taken along line III-III in FIG. 1; FIG. 2 is a cross-sectional view taken along line IV-IV in FIG. 1; It is a graph which shows the improvement effect of direction detection accuracy. It is a graph which shows the directivity improvement effect. 4 is a graph showing the relationship between the width of the shielding surface and the back radiation power; 5 is a graph showing the relationship between groove depth and back radiation power. It is a top view which shows the radar apparatus of 2nd Embodiment. FIG. 10 is a cross-sectional view taken along line XX in FIG. 9; It is a top view which shows the radar apparatus of 3rd Embodiment. 12 is a cross-sectional view taken along line XII-XII in FIG. 11; FIG. It is a top view which shows the radar apparatus of 4th Embodiment. 14 is a cross-sectional view along line XIV-XIV in FIG. 13; FIG.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Constitution]
Exemplary embodiments of the present disclosure are described below with reference to the drawings.

The radar device 1 of the present embodiment is mounted on a vehicle, transmits radiation waves, and receives reflected waves of the radiation waves reflected by objects. The radiated waves are radio waves of a predetermined frequency, and millimeter waves are used, for example. The radar device 1 may include a transmitting/receiving circuit for transmitting/receiving radiated waves and reflected waves, a signal processing section for processing a received signal received by the transmitting/receiving circuit in order to obtain information on surrounding objects, and the like. The radar device 1 is installed, for example, inside a bumper of a vehicle and detects various objects existing around the vehicle.

As shown in FIGS. 1 to 4, the radar device 1 includes an antenna section 2, a housing 3, and a radome 4. FIG. The radar device 1 is fixed to a metal plate surface that is part of the body 5 of the vehicle inside the bumper.

The antenna section 2 includes a rectangular antenna substrate 21 . One of the two surfaces of the antenna substrate 21 is provided with a plurality of antenna elements 22 for transmitting and receiving radio waves. The surface of the antenna substrate 21 on which the antenna element 22 is formed is hereinafter referred to as an antenna surface 23 .

Here, the long side direction of the antenna substrate 21 is the x-axis direction, the short side direction is the y-axis direction, and the axial direction perpendicular to the antenna surface 23 is the z-axis direction. In the following description, the xyz three-dimensional coordinate axes are used as appropriate. However, the side on which the radiation wave is radiated with the antenna surface 23 as a boundary is the plus side of the z-axis, and the opposite side is the minus side of the z-axis. The plus side of the z-axis is also called the front side of the antenna, and the minus side of the z-axis is also called the rear side of the antenna.

A plurality of antenna elements 22 are two-dimensionally arranged along the x-axis direction and the y-axis direction. Each of the plurality of antenna elements 22 arranged in a row along the y-axis direction functions as one array antenna (hereinafter referred to as a unit antenna). That is, the antenna section 2 has a structure in which a plurality of unit antennas are arranged along the x-axis direction. Any one of the plurality of unit antennas is used as a transmitting antenna, and the others are used as receiving antennas. That is, in the radar device 1, the direction of direction detection is the x-axis direction, which is the direction in which the unit antennas are arranged.

However, the mode of the transmitting antennas and receiving antennas is not limited to this, and the number and arrangement of unit antennas used as transmitting antennas and unit antennas used as receiving antennas can be set arbitrarily. Also, all unit antennas may be used as transmitting antennas, or all unit antennas may be used as receiving antennas.

The housing 3 is made of a metal material, has a rectangular parallelepiped appearance, and forms a space for accommodating the antenna section 2 together with the radome 4 . The housing 3 is provided with a housing recess 31 that is a recess for housing the antenna section 2 on one surface. The depth of the housing recess 31 is set to the same size as the thickness of the antenna substrate 21 . The antenna section 2 is fixed so that the surface of the antenna substrate 21 opposite to the antenna surface 23 is in contact with the bottom surface of the housing recess 31 . As a result, the housing 3 acts as a ground pattern for the antenna section 2 . Further, the antenna section 2 is configured such that a gap used for fixing the radome 4 is formed between the side surface, which is a surface along the thickness direction of the antenna substrate 21, and the inner side surface of the housing concave portion 31. , is fixed in the housing recess 31 . The surface of the housing 3 opposite to the surface on which the housing recess 31 is formed serves as a fixing surface to the body 5 .

The width L of the housing edge portion 32 surrounding the housing concave portion 31 is L ≤ λ/4, and the strength required for the housing 3 is ensured, where λ is the wavelength of the radio wave transmitted and received by the antenna section 2. set to size.

In the following, the xyz-axis directions of the antenna substrate 21 are also applied to the radar device 1 in which the antenna substrate 21 is attached to the housing concave portion 31 .
Choke grooves 33, which are grooves extending along the y-axis direction, are provided on two side walls located at both ends of the housing 3 in the x-axis direction (that is, the azimuth detection direction). The depth D of the choke groove 33 is set to D=λ/4. However, it is not strictly necessary to satisfy D=λ/4, and a deviation of about ±25% may be allowed.

The radome 4 has a rectangular parallelepiped outer shape and a box shape with one side open. That is, the radome 4 has a cylindrical portion 42 formed in a rectangular cylindrical shape and a plate-like portion 41 arranged so as to block one opening of the cylindrical portion 42 . The radome 4 is made of a dielectric that allows radio waves transmitted and received by the antenna section 2 to pass therethrough with low loss. However, the dielectric constant of the dielectric is greater than one. In the radome 4, the thickness of the plate-like portion 41, which is the portion facing the antenna surface 23 of the antenna substrate 21, is set to λg/2, where λg is the wavelength within the radome. However, the intra-radome wavelength refers to the wavelength when the radio waves transmitted and received by the antenna section 2 propagate within the radome 4 .

The opening side of the tubular portion 42 of the radome 4 is fixed around the housing recess 31 to cover the housing recess 31 and protect the antenna surface 23 of the antenna section 2 housed in the housing recess 31 . However, at both ends of the radome 4 in the x-axis direction (that is, in the direction of direction detection), as shown in FIG. 3, the inner wall surface of the tubular portion 42 is fixed in contact with the outer wall surface of the housing 3 at both ends thereof. That is, at both ends of the radar device 1 in the y-axis direction, the radome 4 protrudes outward from the housing 3, and at both ends of the radar device 1 in the x-axis direction, the housing 3 protrudes from the housing more than the radome 4. The body edge portion 32 protrudes outward. In the following description, portions of the housing edge portion 32 that protrude from the radome 4 at both ends in the x-axis direction are referred to as barrier portions 11 . The width of the barrier portion 11 (that is, the length of protrusion from the radome 4) is the same as the width L of the housing edge portion 32. As shown in FIG.

The radar device 1 configured in this way is fixed to the vehicle so that the y-axis direction coincides with the vehicle height direction, the x-axis direction coincides with the horizontal direction, and the z-axis direction coincides with the center direction of the detection area. be. The detection area is an area within a predetermined angular range with the center of the antenna surface 23 as the origin and the normal direction of the antenna surface 23 in the xz plane, that is, the z-axis direction is 0°. The predetermined angle range is set to, for example, −60° to +60°, and may be set wider than this. Radiated waves emitted outside the detection area are called unwanted waves.

[1-2. action]
In the radar device 1 , radiation waves radiated from the antenna section 2 are radiated to the outside via the radome 4 . A part of the radiated wave is reflected by the two boundary surfaces of the radome 4, but since the thickness of the radome 4 is set to λg/2, the reflected wave on the inner surface and the reflected wave on the outer surface are cancel each other out, and the reflected wave from the radome 4 toward the antenna section 2 is suppressed. Further, part of the radiation wave is radiated to the outside while undergoing multiple reflection within the radome 4 . Then, radiation is emitted in various directions from the end of the radome 4 , and is also emitted toward the back of the radar device 1 . The unwanted waves radiated in the rearward direction are reflected by the body 5 and radiated forward, causing an error in direction detection by interfering with the radiated waves radiated within the detection area. In particular, unwanted waves entering the body 5 at an angle close to the z-axis (hereinafter referred to as a steep angle) have a great influence.

In the radar device 1 , the barriers 11 provided at both ends in the azimuth detection direction reflect unwanted waves directed toward the body 5 at such steep angles. In addition, the choke grooves 33 act to cancel unnecessary waves that enter the body 5 at a steep angle and pass near the side walls of the housing 3 . That is, since the reflected wave from the choke groove 33 is 180 degrees out of phase with the incident wave to the choke groove 33, it has the effect of canceling out the unnecessary wave.

[1-3. effect]
According to 1st Embodiment detailed above, there exist the following effects.
(1a) According to the radar device 1, by providing the barrier section 11, it is possible to suppress interference waves based on unnecessary waves reflected by the body 5, which are difficult to predict before mounting on the vehicle, and eventually eliminate unnecessary waves. It is possible to suppress the azimuth detection error that occurs as a cause. Although reflected waves from the barrier 11 also cause direction detection errors, since the barrier 11 is a part of the radar device 1, countermeasures can be taken when designing the radar device 1 alone.

(1b) According to the radar device 1, the manufacturing cost can be reduced because the azimuth detection error can be reduced without providing a radio wave absorbing element or the like.
(1c) According to the radar device 1, since the choke groove 33 is provided, it is possible to cancel part of the unnecessary waves directed toward the body 5 without being reflected by the barrier section 11. Therefore, the azimuth detection caused by the unnecessary waves Errors can be further suppressed.

[1-4. measurement]
FIG. 5 shows the result of calculation of the azimuth detection error in the range of −40° to +40° by simulation based on the signal acquired by the antenna section 2 . A solid line is an example of the present disclosure, and a dashed line is a comparative example. In the example, λ=12.4 mm, L=λ/4, and D=λ/4. In the comparative example, the radome 4 is positioned outside the housing 3 in the x-axis direction, which is the azimuth detection direction, as in the y-axis direction, so that the barrier part 11 does not exist. , and furthermore, a structure in which the choke groove 33 does not exist is adopted.

In both Examples and Comparative Examples, the error increases after exceeding ±10°. However, it can be seen that the embodiment has a greater effect of suppressing the azimuth detection error.
FIG. 6 shows the result of measuring the directivity of the antenna section 2. As shown in FIG. It can be seen that the gain in the azimuth of ±90° or more, that is, the gain in the back direction is suppressed in the example, compared to the comparative example, that is, the unwanted wave reflected by the body 5 is suppressed.

FIG. 7 shows the average value of radiation power in the back direction (hereinafter referred to as back radiation power) measured while varying the width L of the barrier portion 11 in the structure of the example. The average value of the back radiation power decreases as L increases when L≦λ/4, and becomes substantially constant when L>λ/4. In other words, regardless of the size of L, the provision of the barrier section 11 has the effect of suppressing the azimuth detection error. Also, it can be seen that even if L>λ/4, the size of the housing 3 only increases, and no further suppression effect can be expected.

FIG. 8 shows the average value of back radiation power measured while changing the depth D of the choke groove 33 in the structure of the example. The average value of the back radiation power becomes minimum in the vicinity of D=λ/4, that is, the effect of suppressing the azimuth detection error is maximized, and the effect of suppressing is lowered even if D is made shorter or longer. Recognize.

[2. Second Embodiment]
[2-1. Difference from First Embodiment]
Since the basic configuration of the second embodiment is the same as that of the first embodiment, differences will be described below. Note that the same reference numerals as in the first embodiment indicate the same configurations, and refer to the preceding description.

In the first embodiment described above, the x-axis direction is set as the azimuth detection direction. In contrast, the second embodiment differs from the first embodiment in that the y-axis direction as well as the x-axis direction is used as the azimuth detection direction, and the shape of the radome 4a is partially changed accordingly.

The radar device 1a of the second embodiment, as shown in FIGS. 9 and 10, includes an antenna section 2, a housing 3, and a radome 4a. However, see FIG. 4 for a cross-sectional view taken along line IV-IV.

In the antenna section 2, the plurality of antenna elements 22 are arranged in the same manner as in the first embodiment. However, the antenna unit 2 can not only detect the azimuth in the x-axis direction by using the same method as in the first embodiment, but also includes an array antenna having a plurality of antenna elements 22 arranged in a row along the x-axis. , it is also possible to detect the azimuth in the y-axis direction.

Both ends of the radome 4a in the x-axis direction project outward by the housing edge 32 more than the housing 3 than the radome 4a, as in the case of the first embodiment shown in FIG. As shown in FIG. 10, both ends of the radome 4a in the y-axis direction are in a state in which the outer wall surface of the cylindrical portion 42 of the radome 4a is in contact with the inner wall surface of the housing recess 31, similarly to the both ends in the x-axis direction. , and the housing 3 is closer than the radome 4a. The housing edge portion 32 protrudes outward.

That is, in the radar device 1a, the entire housing edge portion 32 is provided so as to protrude outward from the radome 4a, and functions as the barrier portion 11. As shown in FIG.
[2-2. effect]
According to the second embodiment described in detail above, the effects (1a) to (1c) of the first embodiment described above are obtained, and the following effects are also obtained.

(2a) According to the radar device 1a, it is possible to obtain the effect of suppressing azimuth detection errors not only in the x-axis direction but also in the y-axis direction.
[3. Third Embodiment]
[3-1. Difference from First Embodiment]
Since the basic configuration of the third embodiment is the same as that of the first embodiment, differences will be described below. Note that the same reference numerals as in the first embodiment indicate the same configurations, and refer to the preceding description.

The third embodiment differs from the first embodiment in the position of the choke groove 33b in the housing 3b.
The radar device 1b of the third embodiment includes an antenna section 2, a housing 3b, and a radome 4, as shown in FIGS. However, see FIG. 3 for a cross-sectional view taken along line III-III.

In the housing 3b, the choke grooves 33b are provided along the y-axis on the front side of the housing edge portions 32 positioned at both ends in the x-axis direction, instead of being provided on the housing sidewalls. .
[3-2. effect]
According to the third embodiment described in detail above, the effects (1a) and (1b) of the first embodiment described above are obtained, and furthermore, the following effects are obtained.

(3a) According to the radar device 1b, part of the unnecessary waves reflected by the barrier 11 can be canceled by the choke grooves 33b, so that azimuth detection errors can be further suppressed.
[4. Fourth Embodiment]
[4-1. Difference from First Embodiment]
Since the basic configuration of the fourth embodiment is the same as that of the first embodiment, differences will be described below. Note that the same reference numerals as in the first embodiment indicate the same configurations, and refer to the preceding description.

The fourth embodiment differs from the first embodiment in the shape of the radome 4c.
The radar device 1c of the fourth embodiment, as shown in FIGS. 13 and 14, includes an antenna section 2, a housing 3, and a radome 4c. However, see FIG. 3 for a cross-sectional view taken along line III-III.

The plate-like portion 41c of the radome 4c facing the antenna surface 23 has inclined portions 411 formed near both ends in the x-axis direction (that is, the azimuth detection direction) so that the plate thickness becomes thinner toward the both ends. The inclined portion 411 is formed so that the inner surface side of the plate-like portion 41c is parallel to the antenna surface 23 and the outer surface side thereof is inclined to change the plate thickness.

[4-2. action]
Part of the radiation wave from the antenna section 2 propagates toward both ends of the radome 4c in the x-axis direction, ie, the inclined section 411, while being repeatedly reflected inside the radome 4c. In the inclined portion 411, the unwanted waves radiated to the outside are greater than those of the portions with a constant plate thickness, and the unwanted waves radiated in the rearward direction from both ends of the radome 4c in the x-axis direction are reduced accordingly.

[4-3. effect]
According to the fourth embodiment described in detail above, the effects (1a) to (1c) of the first embodiment described above are obtained, and the following effects are also obtained.

(4a) In the radar device 1c, unwanted waves radiated toward the rear side are suppressed, so direction detection errors caused by reflected waves from the body 5 can be further suppressed.
[5. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be implemented in various modifications.

(5a) In the above embodiment, the choke grooves 33 and 33b are provided only on either the side wall of the housing 3 or the barrier section 11, but they may be provided on both. Also, the number of choke grooves 33 and 33b is not limited to one at each end in the azimuth detection direction, and a plurality of choke grooves may be provided at each end.

(5b) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or a function possessed by one component may be realized by a plurality of components. . Also, a plurality of functions possessed by a plurality of components may be realized by a single component, or a function realized by a plurality of components may be realized by a single component. Also, part of the configuration of the above embodiment may be omitted. Also, at least part of the configuration of the above embodiment may be added or replaced with respect to the configuration of the other above embodiment.

DESCRIPTION OF SYMBOLS 1, 1a-1c... Radar apparatus 2... Antenna part 3, 3b... Housing 4, 4a, 4c... Radome 5... Body 11... Barrier part 21... Antenna substrate 22... Antenna element 23... Antenna surface 31 Housing concave portion 32 Housing edge portion 33, 33b Choke groove 41, 41c Plate-shaped portion 42 Cylindrical portion 411 Inclined portion.

Claims (9)

An antenna unit (2) having one or more antennas for radiating radio waves and having an antenna surface from which radio waves are radiated ;
radomes (4, 4a, 4c) formed of a material that transmits radio waves emitted by the antenna section and arranged opposite to the antenna surface;
housings (3, 3b) forming a space for housing the antenna unit together with the radome;
with
At least a part of the peripheral edge of the housing surrounding the antenna surface and in contact with the radome has a barrier portion (32) forming the same surface as the antenna surface and protruding outward from the radome. radar equipment. The radar device according to claim 1,
With the antenna surface as a boundary, the side on which the antenna unit radiates radio waves is the front side, and the side opposite to the front side is the back side,
The radome is made of a material with a dielectric constant greater than 1,
The barrier section is provided at a position that blocks at least part of the radar wave emitted from the peripheral edge section of the radome toward the back side. The radar device according to claim 2,
The radar device, wherein the barrier portions are provided at both ends of the radar device in an azimuth detection direction. The radar device according to claim 3,
The radar device, wherein the antenna unit is configured to irradiate radio waves in a range of at least ±60° along the azimuth detection direction, with a normal direction of the antenna surface being 0°. The radar device according to any one of claims 1 to 4,
The radar device, wherein the projection length of the barrier section from the radome is set to 1/4 or less of the wavelength of radio waves transmitted and received by the antenna section. The radar device according to any one of claims 1 to 5,
The radome is
a plate-like portion (41) arranged opposite to the antenna surface;
a tubular portion (42) provided on the periphery of the plate portion and fixed to the housing;
with
The plate-like portion has a plate thickness of 1/2 of the wavelength in the radome,
The radome wavelength is a wavelength within the radome of radio waves transmitted and received by the antenna section. A radar device according to claim 6,
The plate-like portion has an inclined portion (44) whose plate thickness becomes thinner toward the periphery of the plate-like portion. A radar device according to claim 7,
The inclined portion is formed such that an inner surface facing the antenna surface is parallel to the antenna surface, and an outer surface opposite to the inner surface is inclined with respect to the inner surface. The radar device according to any one of claims 1 to 8,
A radar device, wherein a choke groove (33) having a depth of 1/4 of the wavelength of radio waves transmitted and received by the antenna section is formed in the barrier section or the side surface of the housing having the barrier section.

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